Zizhu Yao

Microporous metal-organic framework with dual functionalities for highly efficient removal of acetylene from ethylene/acetylene mixtures

The removal of acetylene from ethylene/acetylene mixtures containing 1% acetylene is a technologically very important, but highly challenging task. Current removal approaches include the partial hydrogenation over a noble metal catalyst and the solvent extraction of cracked olefins, both of which are cost and energy consumptive. Here we report a microporous metal–organic framework in which the suitable pore/cage spaces preferentially take up much more acetylene than ethylene while the functional amine groups on the pore/cage surfaces further enforce their interactions with acetylene molecules, leading to its superior performance for this separation. The single X-ray diffraction studies, temperature dependent gas sorption isotherms, simulated and experimental column breakthrough curves and molecular simulation studies collaboratively support the claim, underlying the potential of this material for the industrial usage of the removal of acetylene from ethylene/acetylene mixtures containing 1% acetylene at room temperature through the cost- and energy-efficient adsorption separation process.

Metal–organic frameworks with a large breathing effect to host hydroxyl compounds for high anhydrous proton conductivity over a wide temperature range from subzero to 125 °C

It is important but still challenging to develop high-performance proton conducting materials for proton exchange membrane fuel cells (PEMFCs), as such materials should meet the following requirements: stable proton-transport pathway over a wide temperature range, high conductivity at work temperature, and small activation energy Ea to maintain high conductivity at start temperature. Here, we firstly demonstrated that flexible metal–organic frameworks (FMOFs) are good hosts to seek out better proton carriers for such high-performance proton conducting materials. A FMOF [Zn3(tz)2(bdc)2]n (FJU-31, Htz = 1H-1,2,3-triazole, H2bdc = terephthalic acid) with high thermal stability up to 400 °C, which can be readily synthesized from the Zn5(tz)6(NO3)4 precursor and H2bdc, has been employed to host various organic hydroxyls as new proton carriers. Three resulting FMOFs Zn3(tz)2(bdc)2@G (FJU-31@G, G = hydroquinone (Hq), cyclohexanol (Ch) or butanol (Bu)) show large breathing effect amplitudes up to 65% and guest-related single-crystal to single-crystal structural transformations by temperature stimulus. Most importantly, FJU-31@Hq hosting hydroquinone with a high melting point and small pKa exhibits a high anhydrous proton conductivity of 2.65 × 10−4 S cm−1, low activation energy Ea of 0.18 eV, and the widest temperature range from −40 to 125 °C for stable proton conduction among the crystalline porous materials.

40-Fold Enhanced Intrinsic Proton Conductivity in Coordination Polymers with the Same Proton-Conducting Pathway by Tuning Metal Cation Nodes.

Three isostructural imidazole-cation-templated metal phosphates (FJU-25) are the first examples to demonstrate that the tuning of metal cation nodes can be an efficient strategy to significantly improve the proton conductivity without changing the structure of the proton-conducting pathway.

A microporous metal–organic framework with polarized trifluoromethyl groups for high methane storage

A novel NbO-type metal-organic framework UTSA-88a with polarized trifluoromethyl groups exhibits a notably high methane storage capacity of 248 cm(3) (STP) cm(-3) (at room temperature and 65 bar) and a working capacity of 185 cm(3) (STP) cm(-3).

A microporous hydrogen-bonded organic framework with amine sites for selective recognition of small molecules

A three-dimensional hydrogen-bonded organic framework with suitable pore sizes and functional amine groups on the pore surfaces has been realized, exhibiting a highly selective recognition towards pyridine over BTX aromatics. The framework transforms during solvent removal, which displays a selective carbon dioxide capture over methane and nitrogen at ambient temperature.

Additive-Induced Supramolecular Isomerism and Enhancement of Robustness in Co(II)-Based MOFs for Efficiently Trapping Acetylene from Acetylene-Containing Mixtures

Although supramolecular isomerism in metal-organic frameworks (MOFs) would offer a favorable platform for in-depth exploring their structure-property relationship, the design and synthesis of the isomers are still rather a challenging aspect of crystal engineering. Here, a pair of supramolecular isomers of Co(II)-based MOFs (FJU-88 and FJU-89) can be directionally fabricated by rational tuning the additives. In spite of the fact that the isomers have the similar Co3 secondary building units and organic linkers, they adopt distinct networks with acs and snw topologies, respectively, which derive from the conformational flexibility of the organic ligands. It is noteworthy that the porous structure of FJU-88 would be collapsed after removal of the solvent from the pores. But FJU-89a shows permanent porosity accompanied with unusual hierarchical micro- and mesopores and superior gas selective adsorption performance. In addition, FJU-89a can efficiently trap C2H2 from C2H2/CO2 and C2H2/CH4 mixture gases through fixed-bed dynamic breakthrough experiments.

Facile synthesis of oxidized activated carbons for high-selectivity and low-enthalpy CO2 capture from flue gas

The prospect of a worsening climatic situation prompts us to develop energy-saving and cost-effective CO2 capture technologies. In this work, three oxidized activated carbons (ACO-n, n is 1–3) were prepared through a facile synthesis approach via oxidation in the presence of KMnO4 and concentrated H2SO4 for 0.5, 1.0 or 2.0 hours. Interestingly, these carbon materials ACO-n can exhibit high CO2 capacity with low adsorption enthalpy and the selectivity toward flue gas can be adjusted by altering the period of oxidation. Among the pristine activated carbon and ACO-n materials, ACO-2 can exhibit the highest CO2 capacity of 3.01 mmol g−1 under ambient conditions with an adsorption enthalpy of only 23.1 kJ mol−1, slightly larger than the CO2 vaporization enthalpy. Its selectivity of 48.5 is double the value of the pristine activated carbon. A column breakthrough experiment was conducted to evaluate the CO2 separation capability on ACO-2 toward a CO2/N2 (15 : 85 v/v) mixture under kinetic flow conditions, which suggests that the oxidized activated carbon made from sustainable sources is promising for CO2 capture.

An Antiferromagnetic Metalloring Pyrazolate (Pz) Framework with [Cu12(µ2-OH)12(Pz)12] Nodes for Separation of C2H2/CH4 Mixture

The search for functional metalloring organic frameworks (MROFs) has been of continuous interest in the fields of both molecular rings and metal–organic frameworks (MOFs) due to their importance in many multifunctional applications. Herein, a hierarchical pyrazolate framework MROF-12 with the topology of the Schlafli symbol {460.66} is reported, which is constructed by an elongated rigid ligand and attractive metalloring cluster nodes [Cu12(μ2-OH)12(Pz)12]. MROF-12 not only adopts the unique functionalities of the metalloring clusters but also inherits the porous properties of MOFs. The large [Cu12(μ2-OH)12(Pz)12] metalloring nodes with the diameter of 12.202 A endow MROF-12 with excellent stability and antiferromagnetism, and they are bridged by linear pyrazolate ligands (H2NDI) to form micro–mesoporous MROF with permanent porosity. The activated sample MROF-12a can exhibit a relatively high Brunauer–Emmett–Teller/Langmuir surface area (460.7/571.9 m2 g−1) as well as pore volume of 0.240 cm3 g−1. Dynamic fixed bed breakthrough experiments indicate that the separation of C2H2/CH4 or CO2/CH4 mixtures can be efficiently achieved through a column packed with MROF-12a solid.

Robustness, Selective Gas Separation, and Nitrobenzene Sensing on Two Isomers of Cadmium Metal–Organic Frameworks Containing Various Metal–O–Metal Chains

Poor stability has been one of the major difficulties affecting to the practical application of metal-organic frameworks (MOFs). In this work, we obtained two 3D structurally isomeric Cd-MOFs, {[Cd6(NH2Me2)2(PTB)4(HCOO)2(H2O)]·(DMF)13·(H2O)4} n (FJU-35) and {[Cd6(NH2Me2)2(PTB)4(HCOO)2]·(DMF)6·(H2O)2} n (FJU-36) (H3PTB = pyridine-2,4,6-tribenzoic acid) containing different CdII-O-CdII chains by varying the addition agents. FJU-35 with coordinated solvent and formate in asymmetric μ3-η1:η2 coordination mode within the CdII-O-CdII chains is vulnerable to external attacks and is apt to collapse after activation, while FJU-36 with no coordinated solvent in the CdII-O-CdII chains but fully protected by the carboxylates from the ligands and the symmetric formate in the coordination mode μ3-η2:η2 is stable, and its activated sample shows efficient separation of C2H2/CH4 and C2H2/CO2 mixtures. Conversely, FJU-35 with more vulnerability is more sensitive to the detection of nitrobenzene than FJU-36.

CCDC 1529718: Experimental Crystal Structure Determination

Related Article: Hailong Wang, Hui Wu, Jinglan Kan, Ganggang Chang, Zizhu Yao, Bin Li, Wei Zhou, Shengchang Xiang, John Cong-Gui Zhao, Banglin Chen||J.Mater.Chem.A|||doi:10.1039/C7TA01364G